Carb Hole Pipes have a tiny hole, usually placed on or near the bowl, allowing the user to control the airflow through the pipe. A carb also helps regulate the temperature and rate of burning in the bowl. Regulating airflow during inhalation controls how much smoke is created and inhaled, as well as how quickly a bowl is cashed or cherried. This will allow you to control the size of hits and can save you money by using your product more efficiently.